jupyter exit error

[Xiaokui Shu]

when shut down a Kestrel kernel notebook, no matter using the shut down button, or terminate jupyter, this error occurs:

Traceback (most recent call last):
  File "/venv/kestrel/lib64/python3.9/site-packages/ipykernel/kernelbase.py", line 328, in process_control
    await result
  File "/venv/kestrel/lib64/python3.9/site-packages/ipykernel/kernelbase.py", line 911, in shutdown_request
    await self._at_shutdown()
TypeError: object NoneType can't be used in 'await' expression